The present invention relates to a printer containing a printhead which is displaceable at the level of a print surface in a main scanning direction and in a sub-scanning direction with respect to a substrate situated in the print surface, and a supply unit for storing the substrate and delivering the substrate for transport to the print surface, which unit includes means to support a core in the vicinity of its ends, such that the core, while being supported, can rotate to unwind the substrate rolled on said core.
A printer of this kind is generally known from the prior art. In this printer, the substrate is stored on a roll, particularly a core on which 50 to 200 meters of a specific type of substrate are rolled. To print the substrate, the substrate is unwound from the core in the printer as required, and the free end is transported to the print surface. There at least a part of the image for printing is formed by moving the printhead with respect to the substrate in the main scanning direction, typically perpendicularly to the direction of transport of the substrate, and simultaneously energising the printhead imagewise. Thus a strip can be printed on the substrate in the width of the writing part of the printhead. After one or more relative movements of the printhead with respect to the substrate over the strip, the substrate is moved in the sub-scanning direction with respect to the printhead, and this is typically the direction of transport of the substrate, so that a new part of the substrate comes to lie on the print surface. Thus a following part of the image can be formed by scanning the printhead over this new part of the substrate. In this way, a part of the substrate in the size of the image for printing can be completely scanned and provided with all the sub-images. These sub-images together form the image for printing. After the image has been printed, the printed part of the substrate is often cut off from the rest of the substrate so that it can be used separately. The printhead can be equipped with one or more individually activatable print modules. A typical example is an inkjet printhead which comprises four print modules, one for each of the colors cyan, magenta, yellow and black. One problem with this known printer is the incidence of visible connection errors between the different sub-images. For example, sub-images which should just adjoin one another frequently overlap or do not have a common border over their complete length. Such faults may have a very disturbing effect on the printed image, particularly in the case of a color printer. It is known from the prior art to use print strategies to mask these faults. A disadvantage of this is that the possibilities of masking are limited and frequently it is not possible to allow for an arbitrary variation in connection errors.